How do I start coaching on Trailwise?

You set up a coaching business, and you do it yourself from /coaching or /become-a-coach. It asks for your legal name, trading name, country, address, VAT position (registered, or exempt as a small business), your VAT or company number, your currency and your invoice prefix. Two of those can never be changed afterwards: your currency and your invoice prefix, because both are printed on documents that have to stay consistent for the whole life of your books. A coach account is always attached to a business; there is no coach without one.